This invention relates to cleaning compositions, especially to surfactant-based compositions having utility in cleaning aluminum surfaces.
Cleaning the exterior surface of modern aircraft is important from the standpoint of both beauty and performance. The aluminum skin is frequently contaminated with engine fuel, carbon and grease, forming a coating which is hardened by exposure to sunlight and air. Even more important than the decrease in aesthetic appeal is the increase in surface roughness, which is felt to cause a substantial increase in the amount of fuel consumption. In some instances, the contaminants actually corrode the aluminum, reducing its structural strength and decreasing the aircraft's margin of safety.
For at least the last two decades, it has been common to clean soiled aircraft surfaces with an aqueous composition containing surfactants, organic solvents, inorganic builders such as phosphates and silicates, and water. The non-aqueous portion of such compositions is typically about 2-4% of their total weight. Although such compositions are effective to a degree in removal of soil, the water-insoluble solvents tend to leave a dulling film and also attack painted insignia. Further, disposal of the spent cleaning solution creates a serious pollution problem. The organic solvents are detrimental to animal life, and the inorganic phosphate builders promote the undesirable growth of algae when disposed of via a sewer system. Perhaps as disturbing as any other aspect of cleaning aircraft, is the fact that the cleaned surface quickly becomes resoiled with the very type of dirt which had been removed.